This invention relates generally to an apparatus for characterization of electrical properties of a semiconductor body, and, in particular, to the measurements of the electrical properties of a semiconductor wafer body using a mercury column as one of the contacts. The use of a mercury column as a non-invasive contact for measurements of the electrical properties of a semiconductor wafer material is well known in the art. Measurements such as dopant density, capacitance-voltage and current-voltage measurements may be accomplished utilizing such a mercury column contact. The mercury column contact provides an alternative to the use of permanent deposited contacts. Fabrication of the permanent contacts as is known in the art is time-consuming, and costly. In .-+.Silicon Epitaxial Wafer Profiling Using the Mercury-Silicon Schottky Diode Differential Capacitance Methods", by Philip S. Schaffer and Thomas R. Lally, Solid State Technology, pp. 229-233, April 1983, is described the use of a mercury column in creating a mercury-Schottky diode for characterizing doping profiles of silicon-epitaxial wafers. In an article by Peter S. Burggraaf, entitled "C-V Plotting, C-T Measuring and Dopant Profiling: Applications and Equipment", Semiconductor International, pp. 29-35, October 1980, is described the use of a bottom contact mercury column such as is manufactured by MSI Electronics for measurements including capacitance-voltage and capacitance-time.
In an article by Albert Lederman entitled "Vacuum Operated Mercury Probe for C-V Plotting and Profiling", Solid State Technology, pp. 123-126, August 1981, is described the use of bottom mounted mercury contacts for replacing aluminum and C-V measurement techniques designed to characterize semiconductor properties.
In German Patent No. 2,741,682, issued to Antoine Torreiter, et al., is disclosed an apparatus for Capacitance-Voltage measurements including a top mounted mercury column where the mercury is contained in a perpendicular capillary above the semiconductor wafer body, and the other contact is a polished surface. The lower meniscus of the mercury column is adjustable by means of a vacuum on the upper end.
Problems may arise with currently available mercury probes which are bottom-mounted below the wafer and require physical contact to a large portion of the wafer top surface. Due to wafer contamination and moving of the back side contact, wafer mapping is not practical with these instruments. In addition, the prior art mercury probe uses a large mercury reservoir which has health implications. Also, currently-used back side contacts may cause microscopic damage to the wafer body being studied.